Power brake booster



March 9, 1965 F. w. BRooKs ETAL 3,172,335

POWER BRAKE BOOSTER Filed Aug. 7, 1961 2 sheets-sheet 1 MalCh 9 1955 F.w. BROOKS ETAL 3,172,335

POWER BRAKE BOOSTER 2 Sheets-Sheet 2 Filed Aug. '7, 1961 INVENTOR5 FRANKw. BROOKS JAMES O. HELVERN BY a/1i- THEIR ATTORNEY United States PatentO M' 3,172,335 POWER BRAKE BOGSTER Frank W. Brooks, Dayton, and James 0.Helvern, Lewisburg, Ghio, assignors to General Motors Corporation,Detroit, Mich., a corporation of Delaware Filed Aug. 7, 1961, Ser. No.129,756 7 Claims. (Cl. 91-369) This invention relates to brake boostersfor power actuation of the brakes of a motor vehicle.

An object of the invention is to provide a power brake booster whereinthe movable wall in the casing of the power unit is fully resilientlysupported.

Another object of the invention is to provide a power brake boosterwherein a movable wall of the power casing includes a rolling diaphragmbetween the movable wall and the power casing and wherein the movablewall is resiliently supported for reciprocal movement in the powercasing by means of resilient elastomeric seal members provided inopposite walls of the power casing so that the movable wall will beguided and supported resiliently by the elastomeric seal members in itsstroke of reciprocation in the power casing.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

1n the drawings:

FIGURE 1 is a longitudinal cross-sectional View of a power brake boosterincorporating features of this invention and illustrating the brakebooster in a retracted or inactive position.

FIGURE 2 is an enlarged cross-sectional view of a portion of FIGURE 1illustrating the support of one end of the movable wall of the brakebooster in a resilient elastomeric seal member.

FIGURE 3 is an enlarged cross-sectional view of another portion ofFIGURE 1 illustrating the support of the opposite end of the movablewall of the brake booster in a resilient elastomeric seal member.

FIGURE 4 is a transverse cross-sectional view taken along line 4 4 ofFIGURE 2.

FIGURE 5 is a transverse cross-sectional view taken along line 5 5 ofFIGURE 3.

The power brake booster of this invention includes a power casing 111comprising two shell members 11 and 12 secured together by a bayonetlock arrangement 13. The casing 1t) includes a pressure differentialresponsive movable wall 15 that divides the power casing into twocompartments 16 and 17 at opposite sides of the movable wall 15. Thecompartment 16 is a constant pressure compartment whereas thecompartment 17 is a variable pressure compartment varying fromsubatmospheric pressure, or vacuum, to atmospheric pressure, compartment16 being connected with a suitable source of subatmospheiic pressure, orvacuum, such as the manifold of an engine of a vehicle on which thedevice is placed through means of a suitable check valve 18 and aconduit fitting 19.

The compartments 16 and 17 are separated one from the other by means ofa rolling diaphragm 20 that has its outer peripheral edge 21 securedbetween the shells 11 and 12, the inner peripheral edge 22 being securedbetween the wall members 23 and 24 of the movable wall 15 therebysealing the edges of the diaphragm against Huid flow between thecompartments 16 and 17.

The rolling diaphragm 29 provides a compartment separation wall that hasa minimum amount of frictional resistance to movement of the movablewall 15 and provides for substantial freedom of movement of the movablewall, but which diaphragm provides little or no support 3,172,335Patented Mar. 9, 1965 lCC for the movable wall in its reciprocalmovement in the casing 10.

Axial support for the movable wall 15 is occasioned by the cylindricalprojections 25 and 26 that extend from opposite sides of the wall 15.The projection 25 extends through the subatmospheric compartment orchamber 16 through a seal member 27 that is made of an elastomericmaterial, such as rubber or synthetic rubber such as neoprene orduprene, or of a resilient plastic material having characteristics ofbodily resilience, to effect a sealing engagement with the cylindricalperipheral surface 28 of the projection or extension 25 that passesthrough an opening 29 in the seal member 27.

The seal member 27 is in the form of an annulus seated within a cupmember 30 which in turn is secured to the wall member 11 by means of ailange member 31 that forms a part of the master cylinder 35, suitablefastening devices such as screws or bolts securing the flange 31 to thewall member 11. The inner peripheral portion of the seal member 27 has ailexible annular lip 32 that engages the periphery 28 of the projection25 to prevent fluid ow along the periphery of the projection.

The master cylinder 35 has the cylinder bore 36 that terminates in theannular end portion 37 that engages the forward face of the seal member27 so as to retain the seal member between the end portion 37 of themaster cylinder and the radial llange portion 3S of the cup member 30.An annular -spaoe or chamber 39 is provided between the axial annularportion of the cup 30 and the end portion 37 of the master cylinder foradmission of atmospheric air through the port 40, the air being filteredby the air lter 41 so that the forward or left-hand face of the sealmember 27 is exposed to atmospheric pressure with the result thatsubatmospheiic pressure present in chamber 16 will be broken at thechamber 42 provided at the rear end of the master cylinder bore 36.

The projection portion 26 on the opposite `side of the movable wall 15extend through a seal member 45 that is made of a material comparable tothat of the material of which seal member 27 is constructed so as toresiliently support the projection 26 by the seal member L15.

The seal member 45 is carried on the shell 12 by means of radiallyflanged portion 46 fitting within a grooved portion 47 in the sealmember 45. The seal member 45 has the inner peripheral `surface of anopening 48 provided with annular grooves 49 adapted to retain alubrieating material therein, the ridges 50 of the grooves 49 engagingthe peripheral surface 51 of the extension 26 to sealingly engage thesurface and prevent iluid leakage to or from the chamber 17 of the brakebooster. The seal member 27 can have similar grooves, if desired.

From the foregoing description, it will be apparent that the solesupport for the movable wall 15 of the brake booster consists of the tworesilient seal members 27 and 45 that are made of a resilient material,such as an elastomeric substance or a plastic material, the seal members27 and 45 providing the support in which projections 25 and 26reciprocate when the movable wall 15 reciprocates within the casing 10as a result of pressure differential being applied -to opposite sides ofthe movable wall. It will also be noted that the extensions 25 and 26 ofthe movable wall 15 are coaxial with each other and with the movablewall as well as being coaxial with the casing 10 so that the unit can beconstructed in a concentric manner.

The movable wall 15 is retained in the position shown in FIGURE 1 of thedrawings by means of the compression spring 52 in the normal retractedposition of the booster unit.

'Ihe wall 15 is provided with an internal chamber that receives apartitioning carrier member 55 that divides the interior chamber of thewall 15 into the two compartments 56 and 57, compartment or chamber 56containing a reaction transmission means S while the compart- 'ment orchamber 57 receives a follow-up control-valve mechanism 60 whichcontrols admission of atmospheric air or of subatmospheric pressure orvacuum to the chamber 17 to regulate pressure differential on oppositesides of the movable Wall and thereby power actuate the Wall for forwardadvancement of the same.

The follow-up control valve mechanism 60 consists of a valve seat member61 reciprocably slidable in an axial bore 62 provided in the carriermember 55 and having -an air valve seat 63 engaging a valve element 64.Valve element 64 is supported on a flexible diaphragm 65 having 'theinner periphery secured to the valve element 64 and the outer peripherysecured between the wall 15 and the carrier 55 for separation of chamber66 from chamber 67 on movement of the valve element between the airvalve seat 63 and the vacuum valve seat 70 provided on the carriermember 55 as an annulus around the valve seat member 60, air valve seat63 also being an annulus on the member 60.

The valve seat member 60 has an extension 71 projecting into a centralaxial bore 72 provided in the projection 26 on the movable wall 15,which extension receives the inner end of an actuating member 75connected by suitable linkage to the brake pedal 76.

A spring 77 normally holds the valve seat member 60 in the positionshown in FIGURE l with the air valve seat 63 engaging valve element 64and holding valve element 64 out of engagement with the vacuum valveseat 70. The opposite end of spring 77 engages a plurality of reactionlevers 80 having their outer ends S1 pivotally supported on the carriermember 55 and their inner ends 82 adapted for engagement with the innerend of the valve seat member 60 when the inner ends are moved in arighthand direction by means of the reaction disc 83 carried on theinner end of the power transmission member or rod 85. i

The power transmission member 85 is slidably received in an axial bore86 provided in the extension 25 of the movable wall 15, axial bore 86preferably being in the form of a spline arrangement to reduce frictionto movement of the member 85 in the bore 86.

The forward end of the power transmission member 85 engages the mastercylinder piston 90 slidably received in the master cylinder bore 36 ofthe master cylinder. The forward end 91 of the master cylinder pistonengages a cup seal 92 held against the piston end 91 by means of acompression spring 93. The opposite end of the compression springengages a residual pressure check valve 94 normally held on a resilientseat element 95 for regulating retention of pressure in the outletpassage 96 and the brake line conduits 97 connected with the wheelcylinders 98 of the brakes 99. The rear end 100 of the master cylinderpiston 90 carries a secondary seal 101 by which fluid is prevented fromescaping from the annular chamber 102 provided between the ends 100 and91 of the piston 90, chamber 102 connecting with the reservoir 105 bymeans of a port 103 in the bottom wall of the reservoir. A secondfilling port 104 is provided in the bottom wall of the reservoir that isjust forward of the cup seal 924 when the master cylinder piston is inthe retracted position shown in FIGURE l of the drawings.

In operation, when the operator of the vehicle moves the brake pedal 76,plunger 75 is moved forward, in a leftward direction as viewed in thedrawing, to move the valve seat member 60 in a left-hand direction withvalve element 64 following the member 60 by urgence of the spring 106until the valve element engages vacuum seat 70` thereby closing chamber66 from communication with chamber 16 that was previously establishedthrough the passage 108 and the port 109 and thereby cutting off supplyof subatmospheric pressure or vacuum to chamber 17 that had previouslybeen conducted to the chamber 4 from chamber 57 through the port 110 inthe wall 24.

Further advancement of the member 60 in a left-hand direction allows thevalve element 64 to remain seated on vacuum seat 70 and air valve seat63 will be disengaged from valve element 64 so that atmospheric air inchamber 67 can then pass through the port 111 into chamber 57 and thencethrough port 110 to chamber 17 to provide pressure for movement of themovable wall 15 in a left-hand direction. This movement of the wall 15causes power plunger to move master cylinder piston 90 in a left-handdirection in the master cylinder and thereby effect displacement of uidunder pressure from the master cylinder into the wheel cylinders of thebrakes. Concurrently creation of hydraulic fluid pressure in the mastercylinder bore 36 causes a reaction force on the power plunger 85 tendingto move reaction disc 83 in a righthand direction as viewed in FIGURE lagainst the reaction levers 50 to pivot them about their outer ends 81and thereby effect engagement of the inner ends with the member 60 whichtransmits reaction or brake feel to the plunger 75, thereby giving theoperator the feeling of applying the brakes.

It will be seen in all operations of the brake booster of this inventionthat movable wall 15 is carried solely by the resilient seal members 27and 45 so as to give minimum resistance to movement of the movable wall,diaphragm 20 also forming a part of the support structure for themovable wall and separating chambers 16 and 17 from one another.

While the embodiments of the present invention as herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

l. A brake booster mechanism, including, a fluid pressure operated motorincluding a casing having a pressure differential responsive movablewail supported therein including a rolling diaphragm between the walland the casing providing for reciprocable movement of the wall in thecasing, said wall having an extension member projecting from each ofopposite sides thereof, said casing having an elastomeric uid sealmember in each of opposite walls thereof respectively receiving the saidextensions for reciprocation therein and providing with said diaphragmthe sole support of said wall.

2. A brake booster mechanism, including, a fluid pressure operated motorincluding a casing having a pressure differential responsive movablewall supported therein including a rolling diaphragm between the walland the casing providing for reciprocable movement of the Wall in thecasing, said wall having an extension member projecting from each ofopposite sides thereof in coaxial alignment and coaxial with said wall,said casing having an elastomeric fluid seal member in each of oppositewalls thereof in coaxial alignment and coaxial with said casing and saidwall respectively receiving the said extensions for reciprocationtherein and providing with said diaphragm the sole support of said wallfor coaxial reciprocation thereof in said casing.

3. A brake booster mechanism, including, a fluid pressure operated motorincluding a Casing having a pressure differential responsive movablewall supported therein including a rolling diaphragm between the walland the casing providing for reciprocable movement of the wall in thecasing, a follow-up control valve means and reaction transfer meanscarried on said wall, said wall having an extension member projectingfrom each of opposite sides thereof, said casing having an elastomericfluid seal member in each of opposite walls respectively receiving thesaid extensions extending through the said seal members to the exteriorof said casing at opposite sides thereof for reciprocation therein andproviding with said diaphragm the sole support of said wall, anactuating member extending through one of said extensions into operableconnections with said follow-up control valve means, and a powertransmission member extending D through the other of said extensionsinto operable connection with said reaction transmission means.

4. A brake booster mechanism constructed and arranged in accordance withthe structure set forth in claim 3 wherein the said extensions on saidwall and said seal members in said casing walls and said actuatingmember and said power transmission member are all in coaxial aiignmentone with the other and coaxial with the said movable wall and saidcasing.

5. A brake booster mechanism, including, a uid pressure operated motorincluding a casing having a pressure diterential responsive movable Wallsupported therein including a rolling diaphragm between the wall and thecasing providing for reciprocable movement of the wall in the easing,said casing having generally parallel spaced walls positioned atopposite sides of said movable Wall, each of said casing walls having anelastomeric iluid seal member carried thereby and provided withcoaxially aligned openings therein, said movable wall having acylindrical projection extending from each of opposite sides thereofthrough the respective seal members in the said openings therein andsupported by the said seal members with the said projections in slidingsealing engagement with the said openings in the said seal members, eachof the said projections on said movable wall having an axial lengthsutiicient to provide for full reciprocal stroke of movement of saidmovable wall in said casing whereby said projections support saidmovable wall in said casing in said seal members in the full stroke ofreciprocation of said movable Wall in said casing, said seal memberstogether With said diaphragm providing the sole support of said movableWall.

6. A brake booster mechansim, including, a uid pressure operated motorincluding a casing having a pressure differential responsive movablewall supported therein including a rolling diaphragm between the Walland the casing providing for reciprocable movement of the wall in thecasing, said casing including Wall members positioned at opposite sidesof said movable wall, a resilient elastomeric seal member in each ofsaid Wall members in coaxial alignment and coaxial with said movablewall and having coaxial cylindrical openings therein, a cylindricalprojection extending from each of opposite sides of said movable wallcoaxial therewith and slidably sealingly received in said openings insaid seal members for resilient sole support thereby of said movablewall in reciprocation in said casing.

7. A brake booster mechanism, including, a luid pressure operated motorincluding a casing having a pressure differential responsive movablewall supported therein including a rolling diaphragm between the walland the casing providing for reciprocable movement of the wall in thecasing, said casing including wall members positioned at opposite sidesof said movable wall, a resilient elastomeric seal member in each ofsaid wall members in coaxial alignment and coaxial with said movablewall and having coaxial cylindrical openings therein, a cylindricalprojection extending from each of opposite sides of said movable wallcoaxial therewith and slidably sealingly received in said openings insaid seal members for resilient sole support thereby or" said movablewall, a follow-up control valve means and reaction transfer meanscarried on said movable wall, said projections on said movable wall eachhaving an axial bore extending through the same, an actuating memberextending through the axial bore in one of said projections intooperable connection with said follow-up control valve means, and a powertransmission member extending through the axial bore of the other ofsaid projections into operable connection with said reactiontransmission means.

References Cited in the file of this patent UNITED STATES PATENTS AyersAug. 22, 1961

1. A BRAKE BOOSTER MECHANISM, INCLUDING, A FLUID PRESSURE OPERATED MOTORINCLUDING A CASING HAVING A PRESSURE DIFFERENTIAL RESPONSIVE MOVABLEWALL SUPPORTED THEREIN INCLUDING A ROLLING DIAPHRAGM BETWEEN THE WALLAND THE CASING PROVIDING FOR RECIPROCABLE MOVEMENT OF THE WALL IN THECASING, SAID WALL HAVING AN EXTENSION MEMBER PROJECTING FROM EACH OFOPPSOSITE SIDES THEREOF, SAID CASING HAVING AN ELASTOMERIC FLUID SEALMEMBER IN EACH